Also known in the art, wireless charging is so-called as an inductive charging, non-contact induction charging which is completed by near-field sensing for inductively coupling, and the power supply device transfers power energy to electric receiver devices. The electric receiver devices receive the power energy for charging its battery, and also for its own operational use. Because the charger transfers power energy to the electric receiver devices by inductive coupling, between the charger and the electric receiver devices are without wires connection and without conductive contacts exposed.
Specifically, the wireless charger has a coil, wherein AC electromagnetic field is generated by the AC via the coil. There is another coil in the electric receiver device for receiving the AC electromagnetic field, and converted into electrical energy for charging its battery for providing power to the device. This scheme is the same as the transformer which a primary winding and a secondary winding are put on the charger and the electric receiver device, respectively. If the distance between the charger and the electric receiver device is farther, it would need to add a resonant inductive coupling.
Wireless charging has the advantages as followings: (i) security: no need of energized contacts to avoid the risk of electric shock; (ii) durability: power transmission components without exposing, and therefore will not be eroded by moisture, oxygen in the air. Because no contacts exist, so there is no mechanical wear and flashover in connection or separation of components; (iii) making medical implant devices more security: in the implanted medical device, it does not damage to the human body's tissue as charging the implanted medical device in the human body, and without the need for wires to charge through the skin and other tissues of the body, eliminating the risk of infection; (iv) convenient: no need for wire connection while charging, as long as the charger is put nearby. Technically, a charger can charge for a plurality of electric receiver devices, in the case where a plurality of electric receiver devices are used without multiples chargers (may be omitted), without a plurality of electrical sockets, and without a plurality of wires wound around each other.
However, the current wireless charging system does not have a mechanism of auto-detection for under-charged electric devices. Mostly, it uses a timing charging method and the timing charging method will create a waste of electricity, and if the under-charged electric device is faulty or damaged it may cause a fire accident.